The present invention generally relates to the field of repairing shrouded turbine blades. In particular, the invention relates to a method of repairing a notch fillet radius of a shrouded turbine blade.
Shrouded turbine blades are often exposed to extreme environments, such as high temperatures and strong vibrations in aircraft engines. In order to withstand such environments, shrouded turbine blades are typically formed of a nickel-based alloy. Additionally, shrouded turbine blades typically include a hardface structure within a notch fillet radius that dissipates the vibrational forces from the surrounding environment. Although the shrouded turbine blade may be wear resistant, the stresses imparted on the shrouded turbine blade and its parts can cause cracks in the weaker areas of the shrouded turbine blade. For example, the notch fillet radius of the shrouded turbine blade can easily form cracks radiating inward from the edge of the notch fillet radius. If left unattended, the heat and vibrational stresses of the environment may cause the crack to continue to extend inward and cause the shrouded turbine blade to break.
One problem with repairing a crack located at an outer edge of the notch fillet radius is that the hardface structure is typically formed of a brittle material, such as a cobalt-based alloy. This is in contrast to the softer nickel-based alloy forming the shrouded turbine blade. Thus, traditional repair techniques are limited to blending techniques to remove the damaged area. Most of these current repair techniques can only repair the notch fillet radius of the shrouded turbine blade if the crack is no more than approximately 0.03 inches deep inward from the outer edge of the notch fillet radius. If the depth of the crack is greater than approximately 0.03 inches, the entire shrouded turbine blade must typically be replaced. This can be a costly process, particularly if there is only a single crack or if only a small percentage of the shrouded turbine blade is damaged. Therefore, it would be desirable to have methods that allow cracks greater than approximately 0.03 inches deep in the notch fillet radius of shrouded turbine blades to be repaired so that more parts could be salvaged.